Alfred Schnittke first studied privately in Vienna (1946–8), where his father was working; this decisive experience was to have a decisive effect on his work as a composer since this exposure to the Austro-German cultural tradition fundamentally influenced his future tastes and approach to form and vocabulary throughout his career. On his return to Russia, Schnittke studied in the Choirmasters’ Department at the October Revolution Music College in Moscow (1949–53) as well as studying theory privately with Iosif Rïzhkin. He later enrolled at the Moscow Conservatory (1953–8, and as a postgraduate 1958–61), where his teachers were Yevgeny Golubev and Nikolay Rakov. Schnittke later observed that his ‘polystylism’ could be traced to the filling of gaps in his musical knowledge during these years. He himself taught instrumentation at the Conservatory for a decade from 1962, and from this time worked as a freelance composer, writing for the theatre and for film as well as concert works. Between 1962 and 1984 he wrote a total of 66 film scores for Mosfilm and other Soviet film companies: this aspect of his life was to have an important technical influence upon his career as a concert composer. During the course of his life he also wrote a large number of articles concerning various issues in contemporary music, and lectured extensively in Russia and Germany.

Though Schnittke’s growing reputation permitted him numerous journeys abroad from the 1980s onwards, before then his trips outside the Soviet Union had been restricted to one in 1967 to hear Dialogue in Warsaw and another in 1977 to Germany and Austria, as a keyboard player with the Lithuanian Chamber Orchestra. His inevitably complicated relationship with the Soviet regime began with the condemnation of his oratorio Nagasaki by the Union of Composers in 1958. He was subsequently well-treated by the Union, and received commissions from the Ministry of Culture and from two opera companies, but when he was asked to conform to a less experimentalist ideal after completing his second opera – ‘African Ballad’ – he no longer enjoyed official approval. Due to the more liberal attitude of the Krushchyov era, Schnittke and other young composers saw formerly sanctioned scores by Western composers; he was thus able to analyze in great detail not only the music of Stravinsky, Schoenberg, Berg and Webern, but also Stockhausen, Nono and Ligeti. These analyses led to his abandonment of serial techniques. At the same time, however, he was constantly attacked in official publications such as Sovetskaya muzïka. After its première in Gor’kiy in 1974, his First Symphony was to all intents and purposes banned from performance in the wake of Khrennikov’s blanket condemnation of it. This situation changed only when Gorbachyov came to power in 1985.

It was precisely from this time onwards, when, paradoxically, he was finally able to travel to attend performances of his works outside the Soviet Union, that Schnittke began to be plagued by health problems, beginning with a serious stroke in June that year. A second occurred in 1991, a year after he had moved to Hamburg, where he was teaching composition as the Hochschule für Musik und Theater, and from that point on Schnittke’s music became more austere and more obviously concerned with mortality. He suffered another stroke in 1994, but did not cease to compose; he died in 1998 in his adopted city of Hamburg.

Later in life Schnittke was the recipient of numerous international prizes and awards, including the Russian State Prize (twice, in 1986 and 1995) and awards from Austria, Germany and Japan. He was made a member of the Academies of Arts of Munich, Stockholm, Hamburg, Berlin and London, and given honorary membership of several others.

The ability to read the score of a complex orchestral composition is by no means a common skill. But even to the untrained eye, the manuscript of the Russian composer Alfred Schnittke’s Symphony No. 9 would speak volumes. Notes are only approximately positioned on the staffs, and their stems are shaky squiggles. Bar lines veer off at a slant. The handwriting, at times nearly illegible, is clearly pained.

“It’s a testament by someone who knows he’s dying,” the conductor Dennis Russell Davies said during a recent interview. “He was determined to finish this piece. You can see and feel this in his shaking hand.”

Mr. Davies, a conductor long associated with Schnittke’s music, will conduct the Juilliard Orchestra in the American premiere of the work at Avery Fisher Hall tonight, in one of only a few appearances here since taking a year off for treatment of Hodgkin’s lymphoma.

Schnittke completed the three-movement symphony in short score before he died in August 1998. But a series of strokes had paralyzed his right side, including his writing hand, preventing him from orchestrating the work. He tried to have the piece completed by others — Mr. Davies would not say who they were — but was not satisfied with their results.

After Schnittke died, Irina Schnittke, his widow, engaged the Russian composer Alexander Raskatov to finish the work. The Dresden Philharmonic provided a partial commission and reached out to Mr. Davies, who conducted the world premiere there in June. Mr. Davies also enlisted the Bruckner Orchestra Linz, of which he is the chief conductor, and the Juilliard School as co-commissioners.

Joseph W. Polisi, the president of the Juilliard School, said the project had particular resonance for Juilliard because it related to an important collection of musical manuscripts the school acquired in March 2006, which included many sketches and manuscripts by Schnittke. “We have become sensitive to his work,” Mr. Polisi said, “and I thought this was a natural parallel.”

Mr. Davies laid a photocopy of Schnittke’s manuscript next to the finished score on a desk and pointed out several places where the original had raised issues. Some combinations of notes created dissonances that were unusual even in Schnittke’s work. Mr. Raskatov occasionally overruled instrumental voicings that Schnittke had indicated.

Mr. Raskatov, born in 1953, had a close personal relationship with Schnittke, Mr. Davies said. The younger composer’s cool, ritualistic music has little in common with the eclecticism and pastiche of Schnittke’s most familiar works. Still, Mr. Davies says the work is faithful to Schnittke’s intentions.

“It’s pretty direct, pretty formidable in its tonal components,” he said. “There’s not time for references to some of the religious and popular elements that he liked to bring into his music.” Some passages unfurl with a weighty Mahlerian melancholy; others echo the ascetic severity of late Shostakovich.

Mr. Raskatov composed an original epilogue, “Nunc Dimittis,” a stark 15-minute meditation based on verses by the Russian poet Joseph Brodsky and an Orthodox monk, Staretz Silouan. Alison Tupay, a mezzo-soprano, and the Hilliard Ensemble will sing the work tonight.

Mr. Davies plans to record both pieces with the Dresden Philharmonic for the ECM label in January and will conduct them in Linz, Austria, in April. Still, after taking the 2005-6 season off for chemotherapy and recovery, he has reduced his travel schedule.

Last month, he conducted Philip Glass’s new opera, “Appomattox,” in San Francisco, then went to Detroit for another premiere, William Bolcom’s Symphony No. 7. But he turned down offers for engagements that would have deviated from his gradual path back to Linz.

His own illness, Mr. Davies asserted, did not affect his approach to the Schnittke piece. “But during my treatment, I was around people who were much worse off than I was and saw how courageous they were,” he said. “Having seen that, then seeing this manuscript and recognizing how desperately the man wanted to write this music, it made my work that much more meaningful.”